GB2200166A

GB2200166A - Pump and method for the assembly thereof

Info

Publication number: GB2200166A
Application number: GB08729718A
Authority: GB
Inventors: Alois Gschwender; Horst Krueger; Bernhard Schleifer
Original assignee: Flux Geraete GmbH
Current assignee: Flux Geraete GmbH
Priority date: 1986-12-24
Filing date: 1987-12-21
Publication date: 1988-07-27
Anticipated expiration: 2007-12-21
Also published as: US4875827A; GB2200166B; GB8729718D0

Description

22- 0 0 16 6 Q r PUMP'AND'METHOD FOR THE ASSEMBLY THEREOF The invention

relates to a-pump,, in particular a drum pump, having a shaft which extends over part of its length in a support tube. in which tube it is rotatably supported by at least one bearing, and to a method for the assembly of such a pump.

In known pumps, a shaft is supported in a support tube by several bearings distributed over its length. They must assume an exact fitted position and have low manufacturing tolerances. Therefore, the manufacture and assembly of such pumps is complicated and expensive.

A pump is also known (German OS 27 50 801), in which a plastic hose is provided as the bearing, which is seated with clearance between the shaft and the support tube. Deposits may form between the plastic hose and the shaft as well as between the plastic hose and the support tube, which deposits cannot be removed towards the outside and cannot be removed with rinsing liquid, and may lead to premature failure of the pump.

It is the object of the invention to simplify the mounting of the shaft in the support tube as regards manufacture and assembly and to construct it so that no deposits may form between the bearing and the shaft.

The invention provides a pump, having a shaft which extends over part of its length in a support tube, in which tube it is rotatably supported by at least one bearing,,.wherein the bearing is constructed inside the support tube as a helix.

The invention also provides a method for the assembly of the pump as aforesaid. in which the bearing is inserted in the support tube and the shaft is pushed in, the bearing, wherein the outer diameter of the helix is reduced by resilient twisting, in the twisted position the helix is pulled into the support tube and then the torsion is discontinued, the helix returning in the direction of its initial position and bearing against the inner wall of the support tube.

The bearing constructed as a helix can be manufactured very easily. The starting material may be a tube from which pieces of tube are cut off. which are then slotted to form the helix. By appropriate rotation at its ends, the diameter of the helix may simply be reduced.by resilient twisting and then easily pulled into its fitted position in the support tube. As soon as the helix has reached its fitted position, twisting of the helix is'discontinued, so that it springs back to its initial position and bears firmly against the inner wall of the support tube. It is then solely necessary to insert the shaft through the helix. If the helix has to be dismantled, its diameter-must solely be reduced by twisting. It can then be easily pulled out of the support tube. As a result of the helical construction, the bearing has a continuous helical interspace. If the pump is removed from the container, the liquid in this interspace may flow out of the support tube. so that the formation of harmful deposits is reliably avoided. If different media are pumped in succession, then there is no mixing of these media, because after removing the pump from the container, each medium immediately flows out.

1 The invention will be described in detail with reference to the drawings, in which:- Figure 1 is an axial section of part of a pump according to the invention, which has to be connected to a 30 drive motor, Figure 2 shows to an enlarged scale and in axial section part of a support tube of a bearing of the pump according to the invention.

Figures 3,4 and 5 show further embodiment of pumps according 35 to the invention, in illustrations according to Figure 1.

i r In 1-i,..,e-drawings, the drive motor of the pump is not shown. The pump part has a casing 1, in which a support tube 2 is arranged coaxially. An annular uptake channel 3 is formed between the inner wall of the casing 1 and the support tube 2, in which channel the liquid to be pumped is conveyed upwards to an outlet 4 in the casing 1. Seated at the upper end of the casing 1 is a screw cap 5, by which this pump part is connected to a connecting member of the drive motor (not shown).

Extending in the support tube 2 is a shaft 6, which supports a rotor 7 in a non-rotary manner at the'lower end. It is located in a rotor chamber 8 at the lower end of the ca,sing 1, into which the uptake channel 3 opens. The support tube 2 is supported in known manner approximately half way along its length with respect to the casing 1. The end of the shaft 6 projecting downwards from the support tube 2 is supported in a rotary manner in a bearing 9. At the upper end, the shaft 2 is supported in a rotary manner by two bearings 10 and 11 lying axially opposite eachother at a distance apart. The upper end of the shaft supports a clutch member 12, by which the shaft can be connected in known manner to the drive shaft of the drive motor.

The shaft 6 has a diameter which is preferably in the range of between approximately 2 mm and approximately 30 mm. In the support tube 2 the shaft 6 is supported by a bearing 13 constructed as a helix. In the embodiment according to Figure 1, the helix 13 extends virtually over the entire length of the support tube 2, so that the shaft 6 is supported in an optimum manner. The helix 13 may also extend sole ly over part of the length of the support tube 2 (Figure 4). It is also possible, particularly if the shaft 6 is relatively long, to provide two or more helices 13 in the support tube 2 (Figure 5). In this case, these helices may adjoin each other directly or even have an axial spacing one from the other. The helix 13 has a helical -4 r, portion 13a, which preferably has a constant pitch over its length, so that the shaft is uniformly supported over the length of the helix. It is quite possible'that the helix 13 has a different pitch ov er its length. Thus, the pitch may increase continuously or even discontinuously from below towards the top or can even decrease from below towards the top. For example, if the pitch of the helix 13 decreases towards the top, then at the lower end it has its largest pitch. If the pump is removed fic-ir- the respective container, then the liquid located between the shaft 6 and 1 may flow out very quickly, because this the support tube liquid is guided over the shortest route from the support tube 2 by the pitch of the helix 13 increasing in the downwards direction. The size and nature of the pitch also eletermine the support length, with respect to a given length of shaft. If the pitch is small, then there are a high number of turns within a given section of length, whereas with a large pitch, a much lower number of turns is located on this length of shaft. An optimum adaptation of the support of the shaft 6 in the support tube 2 is thus possible. In the case of a small diameter of the shaft 6, the pitch 15 of the portion 13a of the helix is small and with a large shaft diameter, correspondingly large. The ratio of the diameter of the shaft 6 to the pitch 15 of the helix portion 13a may amount to approximately 0.07 to approximately 30. In this region, depending on the shaft diameter, the shaft 6 may be supported in a trouble-free manner. This ratio is preferably in the range of between approximately 0.1 and approximately 5.

The pitch of the helix 13 may be left-handed or right- handed (Figures 1 and 3). Since the shaft 6 rotates in only one direction due to this varying nature of the helix it is ensured that in one case the liquid to be pumped along the helix 13 is pushed upwards and in the other case downwards.

If the shaft 6 is to be lubricated in the helix 13, then it is advantageous if the liquid to be pumped along the helix 13 is pushed upwards, so that an optimum lubrication of the p 1 1 Q 1 1 1 - 1) shaft by the medium to be pumped is achieved.

The turns of the portion of the helix 13a are at a distance apart. This forms a helical interspace 14, in which the liquid located in the support tube 2 may flow down- wards without difficulties out of the support tube when the pump is lifted out of the container. The ratio of the diameter of the shaft 6 to the axial width 16 of the interspace 14 is, according to the medium to be pumped, between approximately 0.08 and approximately 50, preferably between approx- imately 0.1 and approximately 7.5. If the medium is relatively viscous, then the width 16 of the interspace 14 is greater than with a medium which has only low viscosity. In each case the interspace 14 is so wide that taking into consideration an optimum support for the shaft 6, the medium in the helical interspace can flow downwards in a trouble free manner when the pump is removed from the container.

In order to vary the capacity of the interspace 14, apart from the width 16, the thickness 17 of the helix portion 13a may also be varied. The thicker the helix portion 13a, the greater the capacity of the interspace 14 for a given width. Also, the medium may flow downwards quickly in a correspondingly large interspace 14.

The ratio of the diameter of the shaft 6 to the thickness 17 of the helix portion 13a may be between approximately 0.4 and approximately 30, preferably between approximately 1 and approximately 7.5.

In order to support the shaft in an optimum manner, the ratio of the diameter of the shaft 6 to the axial width 18 of the helix portion 13a, is between approximately 0.4 and approximately 25, preferably between approximately 0.6 and approximately 7.5.

The helix 13 is preferably installed with respect to the direction of rotation of the shaft 6 so that due to the rotating shaft the helix experiences a force acting in the expanding direction. Consequently, during operation, the helix is pressed by the shaft 6 firmly against the inner wall of the support tube 2.

During the assembly of the pump, the helix 13 is twisted resiliently at its two ends so that its outer diameter is smaller than the inner diameter of the support tube 2. In this twisted state, the helix 13 can be easily pulled into the support tube 2. As soon as the helix 13 has reached its fitted position, the resilient twisting is eliminated, so that the helix springs back into its initial position and thus bears firmly against the inner wall of the support tube 2. In order to ensure reliable retention of the helix 13 in the fitted position, the outer diameter of the helix 13 in the initial state isgreater than the inner diameter of the support tube 2. Consequently, in the fitted position, the helix 13 bears under elastic pre-tension against the inner wall of the support tube 2 and is held reliably. Additional securing members for the axial securing of the helix 13 in the support tube 2 are then not necessary. In the afore- described preferred fitted position of the helix 13 with respect to the direction of rotation of the shaft 6, then during operation, additional security against the displacement of the helix 13 in the support tube 2 is achieved by the rotating shaft.

The helix 13 preferably consists of synthetic material. Polytetrafluoroethylene has proved particularly suitable in this case, which not only has excellent sliding properties, but is also extremely resistant to corrosive media which.are to be pumped.

In place of the polytetrafluoroethylene, a polytetrafluoroethylene compound is possible as the material for the helix 13. Glass fibres, carbon or graphite can be used as constituents of the compound. The glass fibres produce a 1 1 o.

7 0 W1 1 il harder and also a more resilient helix 13, which is characterised by excellent wear properties. The constituents of the compound carbon and graphite on the other hand have good sliding properties and ensure a good dissipa- tion of heat. Thus, depending on the desired conditions of use, the helix 13 can be produced from these various materials.

Claims

CLAIMS 1. A pump,, having a shaft which extends over part of its length in

a support tube. in which tube it is rotatably supported by at least one bearing, wherein the bearing is constructed inside the support tube as a helix.
2. A pump according to claim 1, wherein the pitch of the helix is righthanded.
3. A pump according to claim 1, wherein the pitch of the helix is lefthanded.
4. A pump according to any one of claims 1 to'3,, wherein the helix extends solely over part of the length of the support tube.
5. A pump according to claim 4, wherein at least two helices extend over at least part of the length of the 15 support tube.
6. A pump according to any one of claims 1 to 3, wherein the helix extends over substantially the entire length of the support tube.
7. A pump according to any one of claims 1 to, wherein the helix has a constant pitch over its length.
8. A pump according. to any one of claims 1 to 7, wherein the pitch of the helix is chosen, whereby the shaft expands thetelix as it rotates.
9. A pump according to any one of claims 1 to 8. wherein the helix consists of a-synthetic material.
10. A pump according to claim 9, wherein the helix 11 -1 Y f 1 t - 9 consists of polytetrafluoroethylene.
11. A pump according to any one of claims 1 to 10, wherein the helix bears with elastic pre-tension against the inner wall of the support tube.
12. A pump according to any one of claims 1 to 11, wherein the ratio between the diameter.of the shaft and the pitch of the helix is between 0. 07 and 30.
13. A pump according-to claim 12, wherein the ratio between the diameter of the shaft and the pitch of the helix is between 0.1 and 5.
14. A pump according to any one of claims 1 to 13, wherein the ratio between the diameter of the shaft and the width of a helical interspace of the helix lies between 0.08 and 50.
15. A pump according to claim 14, wherein the ratio between the diameter of the shaft and the width of a helical interspace of the.helix lies between 0.1 and 7.5.
16. A pump according to.any one of claims 1 to 15,, wherein the ratio between the diameter of the shaft and the thickness of a helical portion forming the helix is between 0.4 and'30.
17. A pump according to claim 16, wherein the ratio between the diameter of the shaft and the thickness of.a helical portion forming-the helix is between 1 and 7.5.
18 A pump according to any one of claims 1 to 17, wherein the ratio between the diameter of the shaft and the width of a helical portion forming the helix is between 0A and 25.

- 10,
19. A pump according to claim 18, wherein the ratio between the diameter of the shaft and the width of a helical portion forming the helix is between 0.6 and 7.5.
20. A method for the assembly of the pump according to claim"l, in which the bearing is inserted in the support tube and the shaft is pushed in the.bearing, wherein the outer diameter of the helix is reduced-by resilient twisting. in the twisted position the helix is pulled into the support tube and then the torsion.is discontinued, the helix returning in the direction of its initial position and bearing against the inner wall of the support tube.
21. A pump substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2, Fig. 3, Fig. 4 or Fig. 5 of the accompanying drawings.
22. A method for the assembly of a pump according to claim 21 substantially as hereinbefore described.

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